1. Field of the Invention
Embodiments of the present invention relate generally to a charged particle beam writing apparatus and a charged particle beam writing method, and more specifically, relate to, for example, a writing apparatus and method that performs transmission processing of writing data in real time in accordance with advance of writing processing.
2. Description of Related Art
The lithography technique that advances miniaturization of semiconductor devices is extremely important as a unique process whereby patterns are formed in semiconductor manufacturing. In recent years, with high integration of LSI, the line width (critical dimension) required for semiconductor device circuits is decreasing year by year. For forming a desired circuit pattern on such semiconductor devices, a master or “original” pattern (also called a mask or a reticle) of high accuracy is needed. Thus, the electron beam (EB) writing technique, which intrinsically has excellent resolution, is used for producing such a high-precision master pattern.
FIG. 9 is a conceptual diagram explaining operations of a variable shaped electron beam writing or “drawing” apparatus. The variable shaped electron beam (EB) writing apparatus operates as described below. A first aperture plate 410 has a quadrangular aperture 411 for shaping an electron beam 330. A second aperture plate 420 has a variable shape aperture 421 for shaping the electron beam 330 having passed through the aperture 411 of the first aperture plate 410 into a desired quadrangular shape. The electron beam 330 emitted from a charged particle source 430 and having passed through the aperture 411 is deflected by a deflector to pass through a part of the variable shape aperture 421 of the second aperture plate 420, and thereby to irradiate a target object or “sample” 340 placed on a stage which continuously moves in one predetermined direction (e.g., the x direction) during writing. In other words, a quadrangular shape that can pass through both the aperture 411 of the first aperture plate 410 and the variable shape aperture 421 of the second aperture plate 420 is used for pattern writing in a writing region of the target object 340 on the stage continuously moving in the x direction. This method of forming a given shape by letting beams pass through both the aperture 411 of the first aperture plate 410 and the variable shape aperture 421 of the second aperture plate 420 is referred to as a variable shaped beam (VSB) system.
In an electron beam writing apparatus, it is conventionally performed that writing data input from outside the apparatus is divided per predetermined calculation region so as to be allocated to a plurality of computers, and data conversion processing is performed in parallel in the plurality of computers in order to reduce a processing time for data conversion (refer to, e.g., Japanese Application Laid-open (JP-A) No. 2008-218767). Then, data for which data conversion processing has been performed in parallel is once input into a transmission processing device, and transmitted, in order of writing, to a deflection control circuit. Based on such data, the amount of beam deflection is determined so as to irradiate a target object with a deflected beam.
In a writing apparatus, it is requested to perform data transmission to the deflection control circuit without any delay, and thus to advance writing processing smoothly. However, if data transmission from a transmission processing device to a deflection control circuit is delayed and data for a writing region concerned is disconnected during the writing, the writing processing is once stopped. In an electron beam writing apparatus, when writing is performed while the stage is moving, if transmission of data for writing is delayed and the writing processing is once stopped, the stage position needs to be returned to a position where writing was performed accurately, and then, after the data for writing reaches, writing is started again. Therefore, there is a problem if the operation is once stopped, time needs to be spent in restoring the state from the stopping, which makes the writing time long.